U.S. patent number 6,524,995 [Application Number 09/750,715] was granted by the patent office on 2003-02-25 for catalyst systems of the ziegler-natta type.
This patent grant is currently assigned to Basell Polypropylene GmbH. Invention is credited to Wolfgang Bidell, Rainer Hemmerich, Roland Hingmann, Stephan Huffer, John Lynch, Joachim Rosch, Gunther Schweier, Alexandre Segul, Wolf Spaether, Ingo Treffkorn.
United States Patent |
6,524,995 |
Spaether , et al. |
February 25, 2003 |
Catalyst systems of the Ziegler-Natta type
Abstract
Catalyst systems of the Ziegler-Natta type comprise as active
constituents a) a solid component comprising a compound of titanium
or vanadium, a compound of magnesium, a particulate inorganic oxide
as support and an internal electron donor compound, and as
cocatalyst b) an aluminum compound and c) if desired, a further,
external electron donor compound, wherein the particulate,
inorganic oxide used has a specific surface area of from 350 to
1000 m.sup.2 /g and a mean particle diameter D in the range from 5
to 60 .mu.m and comprises particles which are composed of primary
particles having a mean particle diameter d in the range from 1 to
10 .mu.m and contain voids or channels between the primary
particles, where the macroscopic proportion of voids or channels
having a diameter of greater than 1 .mu.m in the particles of the
inorganic oxides is in the range from 5 to 30% by volume and the
molar ratio of the compound of magnesium to the particulate,
inorganic oxide is from 0.5:1 to 2.0:1.
Inventors: |
Spaether; Wolf (Ilvesheim,
DE), Huffer; Stephan (Ludwigshafen, DE),
Lynch; John (Monsheim, DE), Bidell; Wolfgang
(Mutterstadt, DE), Rosch; Joachim (Ludwigshafen,
DE), Schweier; Gunther (Friedelsheim, DE),
Hingmann; Roland (Barcelona, ES), Segul;
Alexandre (Tarragona, ES), Hemmerich; Rainer
(Grunstadt, DE), Treffkorn; Ingo (Hagenbach,
DE) |
Assignee: |
Basell Polypropylene GmbH
(Mainz, DE)
|
Family
ID: |
7628367 |
Appl.
No.: |
09/750,715 |
Filed: |
January 2, 2001 |
Foreign Application Priority Data
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Jan 21, 2000 [DE] |
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100 02 653 |
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Current U.S.
Class: |
502/341; 502/351;
502/354 |
Current CPC
Class: |
C08F
10/00 (20130101); C08F 10/00 (20130101); C08F
4/025 (20130101); C08F 10/00 (20130101); C08F
4/6546 (20130101); C08F 110/06 (20130101); C08F
110/06 (20130101); C08F 2500/12 (20130101); C08F
2500/24 (20130101) |
Current International
Class: |
B01J
21/10 (20060101); B01J 23/22 (20060101); B01J
21/14 (20060101); B01J 23/02 (20060101); B01J
23/16 (20060101); B01J 21/00 (20060101); B01J
23/06 (20060101); B01J 35/10 (20060101); B01J
35/00 (20060101); C08F 10/00 (20060101); C08F
4/634 (20060101); C08F 110/00 (20060101); C08F
4/18 (20060101); C08F 4/00 (20060101); C08F
10/06 (20060101); C08F 4/654 (20060101); C08F
110/06 (20060101); C08J 5/00 (20060101); C08F
4/642 (20060101); D01F 6/06 (20060101); D01F
6/04 (20060101); B01J 023/02 () |
Field of
Search: |
;502/103,341,351,354
;525/240 ;526/351 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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708459 |
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Feb 1997 |
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AU |
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761 696 |
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Mar 1997 |
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EP |
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0761 696 |
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Mar 1997 |
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EP |
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0 812 861 |
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Dec 1997 |
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EP |
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96/05236 |
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Feb 1996 |
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WO |
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97/48742 |
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Dec 1997 |
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WO |
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97/48743 |
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Dec 1997 |
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WO |
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Primary Examiner: Silverman; Stanley S.
Assistant Examiner: Johnson; Edward M.
Attorney, Agent or Firm: Keil & Weinkauf
Claims
We claim:
1. A catalyst system of the Ziegler-Natta type comprising as active
constituents a) a solid component comprising a compound of titanium
or vanadium, a compound of magnesium, a particulate inorganic oxide
as support and an internal electron donor compound,
and as cocatalyst b) an aluminum compound and c) if desired, a
further, external electron donor compound,
wherein the particulate, inorganic oxide used has a specific
surface area of from 350 to 1000 m.sup.2 /g and a mean particle
diameter D in the range from 5 to 60 .mu.m and comprises particles
which are composed of primary particles having a mean particle
diameter d in the range from 1 to 10 .mu.m and contain voids or
channels between the primary particles, where the macroscopic
proportion of voids or channels having a diameter of greater than 1
.mu.m in the particles of the inorganic oxides is in the range from
5 to 30% by volume and the molar ratio of the compound of magnesium
to the particulate, inorganic oxide is from 0.5:1 to 2.0:1.
2. A catalyst system as claimed in claim 1, wherein the particulate
inorganic oxide used additionally meets at least one of the
following conditions: (I) less than 10% by volume of the primary
particles have a particle diameter d of more than 15 .mu.m or (II)
less than 5% by volume of the primary particles have a particle
diameter d of more than 20 .mu.m.
3. A catalyst system as claimed in claim 1, wherein the particulate
inorganic oxide is obtained by spray drying.
4. A catalyst system as claimed in claim 1, wherein the
particulate, inorganic oxide is an oxide of silicon, aluminum or
titanium or an oxide of a metal of main group I or II of the
Periodic Table or a mixture of such oxides.
5. A catalyst system as claimed in claim 1, wherein the internal
electron donor compound used is a carboxylic ester.
6. A catalyst system as claimed in claim 1, wherein an
organosilicon compound is used as external electron donor compound
c).
7. A catalyst system as claimed in claim 1, wherein the aluminum
compound b) used is a trialkylaluminum.
8. A process for preparing homopolymers of propylene or copolymers
of propylene with one or more other 1-alkenes having up to 10
carbon atoms, wherein the polymerization is carried out in the
presence of a catalyst system as claimed in claim 1.
9. A homopolymer of propylene or a copolymer of propylene with one
or more other 1-alkenes having up to 10 carbon atoms, obtainable by
polymerization of the corresponding monomers in the presence of a
catalyst system as claimed in claim 1.
10. A film, fiber or molding obtainable from a homopolymer of
propylene or a copolymer of propylene with one or more other
1-alkenes having up to 10 carbon atoms as claimed in claim 9.
Description
The present invention relates to novel catalyst systems of the
Ziegler-Natta type comprising as active constituents a) a solid
component comprising a compound of titanium or vanadium, a compound
of magnesium, a particulate inorganic oxide as support and an
internal electron donor compound,
and as cocatalyst b) an aluminum compound and c) if desired, a
further, external electron donor compound,
wherein the particulate, inorganic oxide used has a specific
surface area of from 350 to 1000 m.sup.2 /g and a mean particle
diameter D in the range from 5 to 60 .mu.m and comprises particles
which are composed of primary particles having a mean particle
diameter d in the range from 1 to 10 .mu.m and contain voids or
channels between the primary particles, where the macroscopic
proportion of voids or channels having a diameter of greater than 1
.mu.m in the particles of the inorganic oxides is in the range from
5 to 30% by volume and the molar ratio of the compound of magnesium
to the particulate, inorganic oxide is from 0.5:1 to 2.0:1.
The present invention also relates to a process for preparing
homopolymers and copolymers of propylene with the aid of such
catalyst systems, to the homopolymers and copolymers of propylene
obtainable in this way, to their use for producing films, fibers or
moldings and to the films, fibers or moldings themselves.
WO 96/05236 describes a supported catalyst component comprising a
magnesium halide and, as support, a particulate solid which has a
specific surface area of from 10 to 1000 m.sup.2 /g and in which
the majority of the support particles are in the form of
agglomerates of subparticles. Such catalyst components make it
possible to prepare 1-alkene polymers having a good morphology and
bulk density at high catalyst efficiency.
EP-A 761 696 relates to catalyst systems of the Ziegler-Natta type
comprising, as supports, particulate silica gels which have a mean
particle diameter of from 5 to 200 .mu.m, a mean particle diameter
of the primary particles of from 1 to 10 .mu.m and voids or
channels which have a mean diameter of from 1 to 10 .mu.m and whose
macroscopic proportion by volume in the total particle is in the
range from 5 to 20%. The catalyst systems have a high productivity
and stereospecificity in the polymerization of C.sub.2 -C.sub.10
-alk-1-enes and films produced from such polymers have a reduced
tendency to form microspecks, i.e. small irregularities in the
surface of the films.
WO 97/48742 discloses loosely aggregated catalyst support
compositions which have a particle size of from 2 to 250 .mu.m and
a specific surface area of from 100 to 1000 m.sup.2 /g, where the
support particles comprise particles having a mean particle size of
less than 30 .mu.m and a binder which loosely binds these particles
to one another. The polymerization catalysts obtainable from such
catalyst supports have a high activity and lead to homogeneous
polymers from which films having a good appearance can be
produced.
WO 97/48743 relates to crumbly, agglomerated catalyst support
particles which have a mean particle size of from 2 to 250 .mu.m
and a specific surface area of from 1 to 1000 m.sup.2 /g and which
are produced by spray drying primary particles having a mean
particle size of from 3 to 10 .mu.m. The characteristic feature of
these agglomerated catalyst support particles is that at least 80%
by volume of the agglomerated particles which are smaller than the
D.sub.90 of the original particle size distribution have a
microspherical morphology. (The D.sub.90 indicates that 90% by
volume of the particles have a smaller diameter.) The
microspherical agglomerated catalyst support particles have
interstitial voids of uniform size and distribution within the
particle; at least some of the voids penetrate the particle surface
and thus form at least 10 channels from the surface to the interior
of the agglomerated particles. The polymerization catalysts
obtainable from these catalyst supports also have a high activity
and allow the production of films having a good appearance.
Although the polymers prepared using polymerization catalysts
corresponding to the prior art described by and large meet the
requirements in respect of film quality, the proportion of
microspecks or troublesome impurities is still capable of
significant improvement, especially compared to polymers which have
been produced using catalyst systems containing no inorganic oxides
as support.
Furthermore, in the production of fibers from polymers of
propylene, it is necessary for economic reasons to achieve a
significant increase in the operating lives of the filters for
liquid polypropylene upstream of the spinnerets. These operating
lives are significantly lower in the case of polypropylene which
has been prepared using supported catalysts than in the case of
polypropylene which has been obtained using an unsupported
catalyst.
However, the advantages in respect of polymer morphology which
result from the use of the inorganic oxides should be retained. In
addition, there is always a need to achieve higher catalyst
productivities.
It is an object of the present invention to remedy the
abovementioned disadvantages and to develop improved catalyst
systems of the Ziegler-Natta type which have significantly improved
productivity and which make it possible to obtain polymers of
1-alkenes having a good morphology and a high bulk density from
which it is possible to produce, inter alia, films having a reduced
tendency to form microspecks and fibers having less troublesome
contamination, which leads to an increase in the operating lives of
the polymer melt filtration screens.
We have found that this object is achieved by the catalyst systems
defined at the outset, and also by the process for preparing
polymers of propylene, their use for producing films, fibers or
moldings and also the films and fibers or moldings made of these
polymers.
The catalyst systems of the present invention comprise a solid
component a) and also a cocatalyst. A suitable cocatalyst is the
aluminum compound b). Preferably, in addition to this aluminum
compound b), an electron donor compound c) is additionally used as
a further constituent of the cocatalyst.
According to the present invention, the catalyst system is prepared
using at least one particulate inorganic oxide which has a specific
surface area of from 350 to 1000 m.sup.2 /g, preferably from 400 to
700 m.sup.2 /g and in particular from 450 to 600 m.sup.2 /g,
determined by nitrogen adsorption in accordance with DIN 66131.
The inorganic oxides to be used according to the present invention
have a mean particle diameter D of from 5 to 60 .mu.m, preferably
from 15 to 60 .mu.m and in particular from 20 to 60 .mu.m. Here,
the mean particle diameter D is the volume-based mean (median) of
the particle size distribution determined by Coulter Counter
analysis in accordance with ASTM Standard D 4438.
The particles of the inorganic oxides are composed of primary
particles which have a mean particle diameter d of from 1 to 10
.mu.m, preferably from 3 to 10 .mu.m and in particular from 4 to 8
.mu.m. These primary particles are porous, granular oxide particles
which are generally obtained by dry and/or wet milling from a
hydrogel of the inorganic oxide. It is also possible to sieve the
primary particles before they are processed further.
In addition, the inorganic oxides have voids or channels which have
a diameter of greater than 1 .mu.m and whose macroscopic proportion
in the particles of the inorganic oxides is in the range from 5 to
30% by volume, in particular from 10 to 25% by volume. It is also
advantageous for them to meet at least one of the following
conditions: i) less than 10% by volume and preferably less than 8%
by volume of the primary particles have a particle diameter d of
greater than 15 .mu.m or ii) less than 5% by volume and preferably
less than 3% by volume of the primary particles have a particle
diameter d of greater than 20 .mu.m.
The mean particle diameter d of the primary particles, the
distribution of the particle diameters d of the primary particles
and the macroscopic proportion of the voids or channels having a
diameter of greater than 1 .mu.m are determined by image analysis
of scanning electron micrographs of cross sections of the inorganic
oxide particles. Evaluation is carried out by conversion of the
halftone image obtained by electron microscopy into a binary image
and digital evaluation by means of an appropriate EDP program.
Here, the particles are "electronically" fragmented, i.e. primary
particles which are in contact are separated from one another by
means of a sequence of mathematical operations. It is then possible
to classify the separated particles electronically according to
size and to count them. This gives a precise particle size
distribution of the primary particles and indicates the proportion
of coarse primary particles having particle sizes d of greater than
15 .mu.m or 20 .mu.m in the particulate inorganic oxide examined.
In addition, the precise proportion of voids or channels having a
diameter of greater than 15 .mu.m or 20 .mu.m within the particles
can be determined in the course of the analytical evaluation.
Preferably, at least 100 of the particles composed of primary
particles are analyzed so as to obtain a sufficiently large number
of particles for reproducibly good statistical evaluation. This
means that a number of images of cross sections (scanning electron
micrographs) have to be employed.
The inorganic oxides can be obtained, for example, by spray drying
the milled hydrogels, which are for this purpose mixed with water
or an aliphatic alcohol. Spray drying can be carried out using a
binder which promotes the particle formation process during spray
drying and/or improves the cohesion of the primary particles in the
particles of the inorganic oxide. As binder, it is possible to use
particularly fine, e.g. colloidal, particles of the inorganic
oxides. However, it is also possible to add auxiliaries, for
example polymers such as cellulose derivatives, polystyrene or
polymethyl methacrylate, as binder. The particles obtained in this
way generally have a spheroidal, i.e. sphere-like, shape.
Suitable inorganic oxides are, first and foremost, the oxides of
silicon, aluminum, titanium, zirconium or one of the metals of main
groups I and II of the Periodic Table, or mixtures of such oxides.
Preferred oxides are, for example, aluminum oxide, aluminum
phosphate, magnesium oxide or sheet silicates. Particular
preference is giving to using silicon oxide (silica gel). It is
also possible to use mixed oxides such as aluminum silicates or
magnesium silicates.
The particulate inorganic oxides usually have pore volumes of from
0.1 to 10 cm.sup.3 /g, preferably from 1.0 to 4.0 cm.sup.3 /g,
measured by mercury porosimetry in accordance with DIN 66133 and by
nitrogen adsorption in accordance with DIN 66131.
Depending on the process by which the particulate inorganic oxides
are prepared, their pH, i.e. the negative logarithm to the base ten
of the proton concentration, can assume various values. It is
preferably in the range from 3.0 to 9.0, in particular from 4.0 to
7.5 and particularly preferably from 4.0 to 7.0. The pH of the
particulate inorganic oxides is generally determined by the method
described in S. R. Morrison, "The Chemical Physics of Surfaces",
Plenum Press, New York [1977], page 130 et seq.
After they have been prepared, the inorganic oxides frequently have
hydroxyl groups on their surface. Removal of water makes it
possible to reduce or completely eliminate the content of OH
groups. This can be achieved by thermal or chemical treatment.
Thermal treatment is usually carried out by heating the inorganic
oxide for from 1 to 24 hours, preferably from 2 to 20 hours and in
particular from 3 to 12 hours, at from 250 to 900.degree. C.,
preferably from 600 to 800.degree. C. The hydroxyl groups can also
be removed by chemical means by treating the inorganic oxides with
customary desiccants such as SiCl.sub.4, chlorosilanes or aluminum
alkyls. Preferred inorganic oxides contain from 0.5 to 5% by weight
of water. The water content is usually determined by drying the
inorganic oxide to constant weight at 160.degree. C. under
atmospheric pressure. The weight loss corresponds to the original
water content.
In addition to the particulate inorganic oxide as support, the
solid component a) comprises, inter alia, compounds of titanium or
vanadium.
Titanium compounds used are generally the halides or alkoxides of
trivalent or tetravalent titanium. Titanium alkoxide halide
compounds or mixtures of various titanium compounds are also
possible. Examples of suitable titanium compounds are TiBr.sub.3,
TiBr.sub.4, TiCl.sub.3, TiCl.sub.4, Ti(OCH.sub.3)Cl.sub.3,
Ti(OC.sub.2 H.sub.5)Cl.sub.3, Ti(O--iso--C.sub.3 H.sub.7)Cl.sub.3,
Ti(O--n--C.sub.4 H.sub.9)Cl.sub.3, Ti(OC.sub.2 H.sub.5)Br.sub.3,
Ti(O--n--C.sub.4 H.sub.9)Br.sub.3, Ti(OCH.sub.3).sub.2 Cl.sub.2,
Ti(OC.sub.2 H.sub.5).sub.2 Cl.sub.2, Ti(O--n--C.sub.4
H.sub.9).sub.2 Cl.sub.2, Ti(OC.sub.2 H.sub.5).sub.2 Br.sub.2,
Ti(OCH.sub.3).sub.3 Cl, Ti(OC.sub.2 H.sub.5).sub.3 Cl,
Ti(O--n--C.sub.4 H.sub.9).sub.3 Cl, Ti(OC.sub.2 H.sub.5).sub.3 Br,
Ti(OCH.sub.3).sub.4, Ti(OC.sub.2 H.sub.5).sub.4 or Ti(O--n--C.sub.4
H.sub.9).sub.4. Preference is given to using those titanium
compounds which contain chlorine as halogen. Also preferred are
titanium halides consisting of only halogen and titanium, and among
these especially the titanium chlorides and in particular titanium
tetrachloride. Among the vanadium compounds, particular mention may
be made of vanadium halides, vanadium oxyhalides, vanadium
alkoxides and vanadium acetylacetonates. The vanadium compounds are
preferably in the oxidation states 3 to 5.
In the preparation of the solid component a), additional use is
preferably made of at least one compound of magnesium. Suitable
compounds of magnesium are halogen-containing magnesium compounds
such as magnesium halides, in particular the chlorides or bromides,
or magnesium compounds from which the magnesium halides can be
obtained in a customary manner, e.g. by reaction with halogenating
agents. In the present context, halogens are chlorine, bromine,
iodine or fluorine or mixtures of two or more thereof, with
preference being given to chlorine or bromine and particular
preference being given to chlorine.
Particularly useful halogen-containing magnesium compounds are
magnesium chlorides or magnesium bromides. Examples of magnesium
compounds from which the halides can be obtained are magnesium
alkyls, magnesium aryls, magnesium alkoxides and magnesium
aryloxides and Grignard compounds. Suitable halogenating agents
are, for example, halogens, hydrogen halides, SiCl.sub.4 or
CCl.sub.4 and preferably chlorine or hydrogen chloride.
Examples of suitable halogen-free compounds of magnesium are
diethylmagnesium, di-n-propylmagnesium, diisopropylmagnesium,
di-n-butylmagnesium, di-sec-butylmagnesium, di-tert-butylmagnesium,
diamylmagnesium, n-butylethylmagnesium, n-butyl-sec-butylmagnesium,
n-butyloctylmagnesium, diphenylmagnesium, diethoxymagnesium,
di-n-propyloxymagnesium, diisopropyloxymagnesium,
di-n-butyloxymagnesium, di-sec-butyloxymagnesium,
di-tert-butyloxymagnesium, diamyloxymagnesium,
n-butyloxyethoxymagnesium, n-butyloxy-sec-butyloxymagnesium,
n-butyloxyoctyloxymagnesium and diphenoxymagnesium. Among these,
preference is given to using n-butylethylmagnesium or
n-butyloctylmagnesium.
Examples of Grignard compounds are methylmagnesium chloride,
ethylmagnesium chloride, ethylmagnesium bromide, ethylmagnesium
iodide, n-propylmagnesium chloride, n-propylmagnesium bromide,
n-butylmagnesium chloride, n-butylmagnesium bromide,
sec-butylmagnesium chloride, sec-butylmagnesium bromide,
tert-butylmagnesium chloride, tert-butylmagnesium bromide,
hexylmagnesium chloride, octylmagnesium chloride, amylmagnesium
chloride, isoamylmagnesium chloride, phenylmagnesium chloride and
phenylmagnesium bromide.
Apart from magnesium dichloride and magnesium dibromide, particular
preference is given to using di(C.sub.1 -C.sub.10 -alkyl)magnesium
compounds as magnesium compounds for preparing the particulate
solids.
The preparation of the catalyst systems of the present invention is
preferably carried out using from 0.5 to 2.0 mol, in particular
from 0.5 to 1.5 mol and particularly preferably from 0.5 to 1.0
mol, of the magnesium compounds per mole of the inorganic
oxide.
In addition to the magnesium compounds, it is also possible to use
at least one internal electron donor compound in the preparation of
the particulate solids. Examples of suitable internal electron
donor compounds are monofunctional or polyfunctional carboxylic
acids, carboxylic anhydrides or carboxylic esters, also ketones,
ethers, alcohols, lactones or organophosphorus or organosilicon
compounds.
Preference is given to carboxylic acid derivatives and in
particular phthalic acid derivatives of the formula (I)
##STR1##
where X and Y are each a chlorine or bromine atom or a C.sub.1
-C.sub.10 -alkoxy radical or are together oxygen in an anhydride
function. Particularly preferred internal electron donor compounds
are phthalic esters in which X and Y is a C.sub.1 -C.sub.8 -alkoxy
radical, for example a methoxy, ethoxy, n-propyloxy, isopropyloxy
n-butyloxy, sec-butyloxy, isobutyloxy or tert-butyloxy radical.
Examples of phthalic esters which are preferably used are diethyl
phthalate, di-n-butyl phthalate, diisobutyl phthalate, di-n-pentyl
phthalate, di-n-hexyl phthalate, di-n-heptyl phthalate, di-n-octyl
phthalate and di-2-ethylhexyl phthalate.
Further preferred internal electron donor compounds are diesters of
3- or 4-membered, substituted or unsubstituted
cycloalkane-1,2-dicarboxylic acids, and also monoesters of
substituted benzophenone-2-carboxylic acids or substituted
benzophenone-2-carboxylic acids. As hydroxy compounds in these
esters, use is made of the alkanols customary in esterification
reactions, for example C.sub.1 -C.sub.15 -alkanols or C.sub.5
-C.sub.7 -cycloalkanols, which may in turn bear one or more C.sub.1
-C.sub.10 -alkyl groups, also C.sub.6 -C.sub.10 -phenols.
It is also possible to use mixtures of various electron donor
compounds.
If internal electron donor compounds are used in the preparation of
the particulate solids, use is generally made of from 0.05 to 2.0
mol, preferably from 0.2 to 0.5 mol, of the electron donor
compounds per mole of the magnesium compounds.
Furthermore, the preparation of the particulate solids can also be
carried out using C.sub.1 -C.sub.8 -alkanols such as methanol,
ethanol, n-propanol, isopropanol, n-butanol, sec-butanol,
tert-butanol, isobutanol, n-hexanol, n-heptanol, n-octanol or
2-ethylhexanol or mixtures thereof, among which ethanol is
preferred.
The catalyst systems of the present invention can be prepared by
methods known per se.
The following two-stage process is preferably employed:
In the first step, the inorganic oxide is firstly mixed in an inert
solvent, preferably a liquid alkane or an aromatic hydrocarbon such
as toluene or ethylbenzene, with a solution of the magnesium
compound, after which this mixture is allowed to react for from 0.5
to 5 hours at from 10 to 120.degree. C., generally while stirring.
Subsequently, usually while stirring continually, a halogenating
agent such as chlorine or hydrogen chloride is added in an at least
two-fold molar excess, preferably in an at least five-fold molar
excess, based on the magnesium-containing compound, and the mixture
is allowed to react for from about 30 to 120 minutes. The C.sub.1
-C.sub.8 -alkanol and the transition metal compound, preferably a
titanium compound, and the internal electron donor compound are
then added at from -20 to 150.degree. C. The transition metal
compound and the internal electron donor compound can be added at
the same time as the C.sub.1 -C.sub.8 -alkanol, but it is also
possible firstly to allow the C.sub.1 -C.sub.8 -alkanol to react
with the intermediate for from about 10 to 120 minutes at from 0 to
100.degree. C. Per mole of magnesium, use is made of from 1 to 5
mol, preferably from 1.6 to 4 mol, of the C.sub.1 -C.sub.8
-alkanol, from 1 to 15 mol, preferably from 2 to 10 mol, of the
titanium compound and from 0.01 to 1 mol, preferably from 0.2 to
0.5 mol, of the internal electron donor compound. This mixture is
allowed to react for at least 10 minutes, in particular at least 30
minutes, at from 10 to 150.degree. C., preferably from 60 to
130.degree. C., generally while stirring. The solid obtained in
this way is subsequently filtered off and washed with a C.sub.7
-C.sub.10 -alkylbenzene, preferably ethylbenzene.
In the second step, the solid obtained from the first step is
extracted with excess titanium tetrachloride or an excess of a
solution of titanium tetrachloride in an inert solvent, preferably
a C.sub.7 -C.sub.10 -alkylbenzene, at from 100 to 150.degree. C. In
the case of a solution, this contains at least 5% by weight of
titanium tetrachloride. The extraction is generally carried out for
at least 30 minutes. The product is then washed with a liquid
alkane until the titanium tetrachloride content of the washings is
less than 2% by weight.
The solid component a) preferably has a molar ratio of the
inorganic oxide to the compound of titanium or vanadium in the
range from 1000 to 1, in particular from 100 to 2 and particularly
preferably from 50 to 3.
An advantage of the catalyst systems of the present invention is
that films of 1-alkene polymers prepared using these catalyst
systems have fewer microspecks, and the fiber products obtained
therefrom display a reduction in troublesome impurities, which
results in an increase in the operating lives of the polymer melt
filtration screens. However, this is not associated with a decrease
in the catalyst productivity, but instead an increased productivity
is observed. With regard to the film quality, it is assumed that
the microspecks are to at least some extent caused by large,
unfragmented solid particles. It should be thus be possible to
reduce the number of microspecks by reducing the mean particle size
d of the primary particles. In actual practice, however, solids
consisting exclusively of very small primary particles and having a
high proportion of colloidal inorganic oxide have a high packing
density which prevents immobilization of the active component owing
to the lack of pores and channels, so that both an increase in the
microspecks and a decrease in the catalyst productivity are
observed.
The use of porous inorganic oxides having the above-described
properties enables the immobilization capacity of the active
components, i.e. the magnesium chloride, the titanium compound and
the electron donor, to be greatly increased, as a result of which
the active components are distributed more homogeneously over the
inorganic oxide matrix and the amount of inorganic oxide as a
proportion of the total particulate solid component a) can be
reduced.
Furthermore, use of inorganic oxides having a reduced mean particle
diameter (of the agglomerate) enables a further significant
improvement in the immobilization capacity of the active component
and thus an increase in the productivity compared to an inorganic
oxide having the same primary particle distribution and the same
morphological structure but a greater mean particle diameter (of
the agglomerate) to be achieved.
The catalyst systems of the present invention can be used, in
particular, for the polymerization of 1-alkenes. The 1-alkenes
include, inter alia, linear or branched C.sub.2 -C.sub.10
-alk-1-enes, in particular linear C.sub.2 -C.sub.10 -alk-1-enes
such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,
1-heptene, 1-octene, 1-nonene, 1-decene or 4-methyl-1-pentene. It
is also possible to polymerize mixtures of these 1-alkenes.
In addition to the solid component a), the catalyst systems of the
present invention further comprise at least one cocatalyst. A
suitable cocatalyst is the aluminum compound b). Preference is
given to using an external electron donor compound c) in addition
to this aluminum compound b).
Suitable aluminum compounds b) are trialkylaluminums and also
compounds which are derived therefrom and in which an alkyl group
is replaced by an alkoxy group or by a halogen atom, for example
chlorine or bromine. The alkyl groups can be identical or
different. Linear or branched alkyl groups are possible. Preference
is given to using trialkylaluminum compounds whose alkyl groups
each have from 1 to 8 carbon atoms, for example trimethylaluminum,
triethylaluminum, triisobutylaluminum, trioctylaluminum or
methyldiethylaluminum or mixtures thereof.
In addition to the aluminum compounds b), it is possible to use
external electron donor compounds c) as further cocatalysts, for
example monofunctional or polyfunctional carboxylic acids,
carboxylic anhydrides and carboxylic esters, also ketones, ethers,
alcohols, lactones and organophosphorus and organosilicon
compounds. The external electron donor compounds c) can be
identical to or different from the internal electron donor
compounds used for preparing the catalyst solid a). Preferred
external electron donor compounds c) are organosilicon compounds of
the formula (II)
where R.sup.1 are identical or different and are each a C.sub.1
-C.sub.20 -alkyl group, a 5- to 7-membered cycloalkyl group which
may in turn bear C.sub.1 -C.sub.10 -alkyl groups as substituents, a
C.sub.6 -C.sub.18 -aryl group or a C.sub.6 -C.sub.18 -aryl-C.sub.1
-C.sub.10 -alkyl group, R.sup.2 are identical or different and are
each a C.sub.1 -C.sub.20 -alkyl groups and n is 1, 2 or 3.
Particular preference is given to compounds in which R.sup.1 is a
C.sub.1 -C.sub.8 -alkyl group or a 5- to 7-membered cycloalkyl
group and R.sup.2 is a C.sub.1 -C.sub.4 -alkyl group and n is 1 or
2.
Among these compounds, particular mention should be made of
diisopropyldimethoxysilane, isobutylisopropyldimethoxysilane,
diisobutyldimethoxysilane, dicyclopentyldimethoxysilane,
dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane,
isopropyl-tert-butyldimethoxysilane,
isobutyl-sec-butyldimethoxysilane and
isopropyl-sec-butyldimethoxysilane.
The compounds b) and c) acting as cocatalysts can be allowed to act
either individually, in succession in any order or together as a
mixture on the catalyst solid a). This usually occurs at from 0 to
150.degree. C., in particular from 20 to 90.degree. C., and
pressures of from 1 to 100 bar, in particular from 1 to 40 bar.
The cocatalysts b) are preferably used in such an amount that the
atomic ratio of aluminum from the aluminum compound b) to the
transition metal from the catalyst solid a) is from 10:1 to 800:1,
in particular from 20:1 to 200:1.
The catalyst systems comprising a catalyst solid a) and, as
cocatalysts, at least one aluminum compound b) or at least one
aluminum compound b) and at least one further electron donor
compound c) are very useful for the preparation of propylene
polymers, both homopolymers of propylene and copolymers of
propylene with one or more other 1-alkenes having up to 10 carbon
atoms. For the purposes of the present invention, the copolymers
may be ones in which the other 1-alkenes having up to 10 carbon
atoms are randomly incorporated. The comonomer content is then
generally less than 15% by weight. However, it is also possible for
the propylene copolymers to be in the form of block copolymers or
impact-modified copolymers. These generally comprise at least one
matrix of a propylene homopolymer or a random propylene copolymer
with less than 15% by weight of other 1-alkenes having up to 10
carbon atoms and a soft phase made up of a propylene copolymer
containing from 15 to 80% by weight of other 1-alkenes having up to
10 carbon atoms in copolymerized form. Preferred comonomers are in
each case ethylene or 1-butene. However, it is also possible to use
mixtures of comonomers, so that, for example, terpolymers of
propylene are obtained.
The preparation of the propylene polymers can be carried out in the
customary reactors suitable for the polymerization of 1-alkenes,
either batchwise or preferably continuously, for example in
solution, as a suspension polymerization or as a gas-phase
polymerization. Examples of suitable reactors are continuously
operated stirred reactors, loop reactors, fluidized-bed reactors or
horizontally or vertically stirred powder bed reactors. Of course,
the reaction can also be carried out in a plurality of reactors
connected in series. The reaction time depends critically on the
reaction conditions selected in each case. It is usually from 0.2
to 20 hours, mostly from 0.5 to 10 hours.
The polymerization is generally carried out at from 20 to
150.degree. C., preferably from 50 to 120.degree. C. and in
particular from 60 to 90.degree. C., and a pressure of from 1 to
100 bar, preferably from 15 to 40 bar and in particular from 20 to
35 bar.
The molar mass of the propylene polymers formed can be controlled
by addition of regulators customary in polymerization technology,
for example hydrogen, and adjusted over a wide range. It is also
possible for inert solvents such as toluene or hexene, inert gases
such as nitrogen or argon and relatively small amounts of
polypropylene powder to be additionally used.
The mean molar masses (weight average) of the propylene polymers
are generally in the range from 10,000 to 1,000,000 g/mol and the
melt flow rates (MFR) are in the range from 0.1 to 100 g/10 min,
preferably from 0.5 to 50 g/10 min. The melt flow rate corresponds
to the amount of polymer which is extruded over a period of 10
minutes from the standardized test apparatus specified in ISO 1133
at 230.degree. C. under a weight of 2.16 kg.
Compared to previously known catalyst systems, the catalyst systems
of the present invention make it possible to prepare 1-alkene
polymers which have a good morphology and a high bulk density and
which tend to form significantly fewer microspecks in film
production. Furthermore, they effect a reduction in the pressure
rise during melt filtration. In addition, the productivity of the
catalyst systems of the present invention is increased.
Owing to their good mechanical properties, the polymers obtainable
using the particulate solids according to the present invention, in
particular the homopolymers of propylene or copolymers of propylene
with one or more other 1-alkenes having up to 10 carbon atoms, are
suitable for the production of films, fibers or moldings and
especially for the production of films.
EXAMPLES
To characterize the products, the following tests were carried
out:
Determination of the Mean Particle Diameter D To determine the mean
particle diameter D of the silica gels, the particle size
distribution of the silica gel particles was determined by Coulter
Counter analysis in accordance with ASTM Standard D 4438 and the
volume-based mean (median) was calculated therefrom.
Determination of the Mean Particle Diameter d of the Primary
Particles, the Distribution of the Particle Diameters d of the
Primary Particles and the Macroscopic Proportion of Voids or
Channels Having a Diameter of Greater Than 1 .mu.m The
determination of the mean particle diameter of the primary
particles, the distribution of the particle diameters d of the
primary particles and the macroscopic proportion of voids or
channels having a diameter of greater than 1 .mu.m in the silica
gels used was carried out by means of scanning electron microscopy
on cross sections of silica gel particles. The electron micrographs
obtained were converted into a binary image and the particles were
"electronically" fragmented by means of the analysis software
package from SIS. The separated particles were electronically
classified according to size and counted. About 200 particles in
each case were used to calculate the particle size distribution of
the primary particles, from which the mean particle diameter d, the
proportion of particles having a diameter d of greater than 20
.mu.m, the proportion of particles having a diameter d of greater
than 15 .mu.m and the proportion of primary particles having
particle diameters d of less than 5 .mu.m was derived. In addition,
the precise proportion of voids or channels having a diameter of
greater than 1 .mu.m within the particles was determined.
Determination of the Specific Surface Area By nitrogen adsorption
in accordance with DIN 66131
Determination of the Pore Volume By mercury porosimetry in
accordance with DIN 66133
Determination of the pH The pH of the silica gel was determined by
means of the method described in S. R. Morrison, "The Chemical
Physics of Surfaces", Plenum Press, New York [1977], page 130 et
seq.
Determination of the Water Content To determine the water content,
5 g of silica gel were dried for 120 minutes at 160.degree. C.
under atmospheric pressure (to constant weight). The weight loss
corresponded to the original water content.
Determination of the Productivity The productivity is the amount of
polymer in gram which was obtained per gram of titanium-containing
solid component a) used.
Determination of the Melt Flow Rate (MFR) ISO Standard 1133, at
230.degree. C. and under a weight of 2.16 kg.
Determination of the Number of Microspecks The number of
microspecks per unit area was determined optically on-line during
film production by means of a Brabender CCD camera.
Determination of the Pressure Rise During Melt Filtration The
determination of the pressure rise during melt filtration is
carried out by extrusion of the polypropylene products in a
standard laboratory extruder (3-zone screw) at 265.degree. C.
through a metal filter disk with a support mesh having a mesh
opening of 5 .mu.m at a throughput of 2 kg/h. The pressure rise at
equal polypropylene throughputs is recorded as a function of
time.
Example 1
1. Preparation of the Catalyst Solid
As inorganic particulate oxide, use was made of a spheroidal silica
gel (SiO.sub.2) having a mean particle diameter D of 60 .mu.m and a
proportion of voids or channels having a diameter of greater than 1
.mu.m of 17.4% by volume. The mean particle diameter d of the
primary particles was 6.1 .mu.m. The primary particles had a narrow
particle size distribution, which was reflected in the fact that
the proportion of particles having a particle diameter d of greater
than 15 .mu.m was only 7.8% by volume, that of particles having a
particle diameter d of greater than 20 .mu.m was only 2.2% by
volume and that of particles having a particle diameter d of less
than 5 .mu.m was only 38% by volume. The silica gel also had a
specific surface area of 505 m.sup.2 /g, a pore volume of 1.8
cm.sup.3 /g, a pH of 5.5 and a water content of 2.1% by weight.
The silica gel was admixed with a solution of n-butyloctylmagnesium
in a mixture of n-heptane and ethylbenzene (heptane content: 33%),
using 0.5 mol of the magnesium compound per mole of SiO.sub.2. The
mixture was stirred for 30 minutes at 95.degree. C., then cooled to
20.degree. C., after which 10 times the molar amount, based on the
organomagnesium compound, of hydrogen chloride was passed in. After
60 minutes, the reaction product was admixed with 2.5 mol of
ethanol per mole of magnesium while stirring continually. This
mixture was stirred for 0.5 hour at 80.degree. C. and subsequently
admixed with 6.0 mol of titanium tetrachloride and 0.45 mol of
di-n-butyl phthalate, in each case based on 1 mol of magnesium. The
mixture was subsequently stirred for 1 hour at 100.degree. C., and
the solid obtained in this way was filtered off and washed a number
of times with ethylbenzene.
The solid product obtained was extracted for 3 hours at 125.degree.
C. with a 10% strength by volume solution of titanium tetrachloride
in ethylbenzene. The solid product was then separated from the
extractant by filtration and washed with n-heptane until the
extractant contained only 0.3% by weight of titanium
tetrachloride.
The catalyst solid a) prepared in this way contained 4.1% by weight
of Ti 8.3% by weight of Mg 33.4% by weight of Cl.
1.2 Polymerization
In a vertically stirred gas-phase reactor having a utilizable
capacity of 800 l, propylene was polymerized in the presence of
hydrogen as molar mass regulator. The reactor contained an agitated
fixed bed of finely divided polymer. The output of polymer from the
reactor was 150 kg of polypropylene per hour.
Gaseous propylene was passed into the gas-phase reactor at
80.degree. C. and a pressure of 32 bar. At a mean residence time of
1.5 hours, polymerization was carried out continuously with the aid
of the catalyst solid a) described under 1.1, using 6.5 g/h of the
catalyst solid a), 300 mmol/h of triethylaluminum b) and 7.5 mmol/h
of isobutylisopropyldimethoxysilane c) as cocatalyst. A
productivity based on the catalyst solid a) of 24,000 g of
polypropylene/g of solid component was achieved.
The gas-phase polymerization gave a propylene homopolymer having a
melt flow rate (MFR) of 10 g/10 min.
1.3 Production of an Extruded Film
A 40 .mu.m thick extruded film was produced from the propylene
homopolymer obtained under 1.2 by means of a single-screw extruder
at a melt temperature of 190.degree. C. and a throughput of 2.5
kg/h. The film obtained had 760 microspecks per m.sup.2.
Example 2
The preparation of the catalyst solid a) is carried out using the
same procedure as in Example 1, except that the mean particle
diameter of the silica gel used is 45 .mu.m, the macroscopic
proportion of pores and channels having a diameter of greater than
1 .mu.m is 16.3% by volume, the mean particle diameter of the
primary particles is 6.3 .mu.m and the proportion of the primary
particles having a particle diameter d of greater than 20 .mu.m or
15 .mu.m is 1.5% or 5.4%, respectively. The proportion of primary
particles having a particle diameter d of less than 5 .mu.m is 43%
by volume. Furthermore, the silica gel has a specific surface area
of 521 m.sup.2 /g (BET), a pore volume of 1.69 ml/g, a pH of 5.5
and a water content of 2.1% by weight. 0.67 mol of magnesium
compound was used per mole of silica gel.
The catalyst solid a) prepared in this way contained: 4.1% by
weight of Ti 10.0% by weight of Mg 36.7% by weight of Cl
The polymerization of propylene was carried out in the same way as
described in Section 1.2 of Example 1.
Example 3
The preparation of the catalyst solid a) is carried out by the same
procedure as in Example 1, except that the mean particle diameter
of the silica gel used is 20 .mu.m, the macroscopic proportion of
pores and channels having a diameter of greater than 1 .mu.m is
16.9% by volume, the mean particle diameter of the primary
particles is 4.2 .mu.m and the proportion of primary particles
having a particle diameter d of greater than 20 .mu.m or 15 .mu.m
is 0.8% or 4.3%, respectively. The proportion of primary particles
having a particle diameter d of less than 5 .mu.m is 64% by volume.
Furthermore, the silica gel has a specific surface area of 495
m.sup.2 /g (BET), a pore volume of 1.74 mg/g, a pH of 5.5 and a
water content of 2.1% by weight. 1.0 mol of magnesium compound was
used per mole of silica gel.
The catalyst solid a) prepared in this way contained: 3.8% by
weight of Ti 10.9% by weight of Mg 40.6% by weight of Cl
The polymerization of propylene was carried out in the same way as
described in Section 1.2 of Example 1.
Comparative Example A
The preparation of the catalyst solid a) is carried out using the
same procedure as in Example 1, except that the mean particle
diameter of the silica gel used is 45 .mu.m, the macroscopic
proportion of pores and channels having a diameter of greater than
1 .mu.m is 6.7% by volume, the mean particle diameter of the
primary particles is 8.5 .mu.m and the proportion of primary
particles having a particle diameter d of greater than 20 .mu.m or
15 .mu.m is 7.7% or 17.4%, respectively. The proportion of primary
particles having a particle diameter d of less than 5 .mu.m is
15.4% by volume. Furthermore, the silica gel has a specific surface
area of 309 m.sup.2 /g (BET), a pore volume of 1.36 ml/g, a pH of
5.9 and a water content of 2.3% by weight. 0.37 mol of magnesium
compound was used per mole of silica gel.
The catalyst solid a) prepared in this way contained: 3.5% by
weight of Ti 7.5% by weight of Mg 28.4% by weight of Cl
The polymerization of propylene was carried out in the same way as
described in Section 1.2 of Example 1.
Comparative Example B
The preparation of the catalyst solid a) was carried out using the
same procedure as in Example 1, except that the mean particle
diameter of the silica gel used is 80 .mu.m, the macroscopic
proportion of pores and channels having a diameter of greater than
1 .mu.m is 18.3% by volume, the mean particle diameter of the
primary particles is 7.1 .mu.m and the proportion of primary
particles having a diameter d of greater than 20 .mu.m or 15 .mu.m
is 2.5% or 9.1%, respectively. The proportion of primary particles
having a particle diameter d of less than 5 .mu.m is 27% by volume.
Furthermore, the silica gel has a specific surface area of 516
m.sup.2 /g (BET), a pore volume of 1.69 ml/g, a pH of 5.5 and a
water content of 2.1% by weight. 0.5 mol of magnesium compound was
used per mole of silica gel.
The catalyst solid a) prepared in this way contained: 3.4% by
weight of Ti 8.0% by weight of Mg 34.7% by weight of Cl
The polymerization of propylene was carried out in the same way as
described in Section 1.2 of Example 1.
The results of the measurements on the propylene homopolymer
obtained in Examples 1 to 3 and in Comparative Examples A and B are
shown in the following table.
Compara- Compara- Example Example Example tive Ex- tive Ex- 1 2 3
ample A ample B Mean 60 45 20 45 80 particle diameter (D) [.mu.m]
Mg/SiO.sub.2 0.5 0.67 1.0 0.37 0.5 ratio [mol/mol] (max.) Specific
sur- 505 521 495 309 516 face area (BET) [m.sup.2 /g] Proportion of
17.4 16.3 16.9 6.7 18.3 channels and pores > 1 .mu.m (% by
volume) Mean 6.1 6.3 4.2 8.5 7.1 primary particle diameter (d)
[.mu.m] Proportion 2.2 1.5 0.8 7.7 2.5 with D > 20 .mu.m (% by
volume) Proportion 7.8 5.4 4.3 17.4 9.1 with D > 15 .mu.m (% by
volume) Proportion 38 43 64 15.4 27 with D < 5 .mu.m (% by
volume) Productivity 24,000 27,000 29,000 18,000 22,000 [g of PP/g
of catalyst solid] Melt flow 10 10 9.3 12 12 rate MFR [g/10 min]
Number of 760 530 360 4995 970 microspecks [per m.sup.2 ] Pressure
rise 20 13 5 34 22 during melt filtration [bar/kg PP]
The silica gels used in Examples 1 to 3 have a comparable
morphology in respect of the composition and the primary particle
distribution, taking into account the different agglomerate
diameters. Specific surface areas and the macroscopic proportion of
pores and channels having a diameter of more than 1 .mu.m are all
in the same range, so that the size effect of the agglomerates is
particularly clear in Examples 1, 2 and 3. The loading capacity of
the silica gel with active component is exploited right up to the
maximum in Examples 1,2 and 3. It becomes clear that as the
agglomerate diameter decreases below 60 .mu.m, the ratio of
magnesium compound (=part of the active component) to silica gel
support can be increased significantly, which is reflected in a
significant rise in the productivity in the polymerization of
propylene. Furthermore, the improved removal of the heat of
polymerization (ratio of surface area to volume increases as the
agglomerate diameter drops) enables the catalyst to maintain its
productivity better over the polymerization time.
A further positive effect of a smaller agglomerate diameter and
increased loading is the reduction in the number of microspecks,
which is also reflected in reduced pressure increases during melt
filtration (a higher pressure increase means a poorer polymer
quality).
Comparison of Examples 1 to 3 according to the present invention
and comparative Examples A and B indicates that, inter alia, the
catalyst system of the present invention displays an increased
productivity compared to the catalyst systems of the prior art. The
propylene homopolymers resulting from Examples 1 to 3 also have a
greatly reduced number of microspecks, which is very advantageous
for the production of films. The quality of the propylene
homopolymer obtained in Examples 1 to 3 according to the present
invention is also demonstrated by the relatively low pressure
increase during melt filtration, which is advantageous in the
production of fiber products.
* * * * *